Middle distillate fuel oil compositions having improved pumpability

ABSTRACT

Fuel oil compositions, containing a pour depressant to provide a pour point below 0*F., exhibit improved pumpability as a result of the inclusion of a minor amount of certain styrenebutadiene copolymers.

United States Patent 1191 Mieville Apr. 30, 1974 MIDDLE DISTILLATE FUEL 01L 3,419,365 12/1968 COMPOSITIONS HAVING IMPROVED PUMPABIUTY 3:467:597 9/1969 Inventor: Rodney L. Mieville, Evanston, Ill.

Assignee: Standard Oil Company, Chicago, 111.

Filed: Jan. 18, 1971 Appl. No.: 107,509

Related US. Application Data Continuation-impart of Ser. No. 770,077, Oct. 23, 1968, abandoned.

us. (:1. 44/62, 44/80 1m. c1 c101 1/18 Field of Search 44/70, 62

References Cited UNITED STATES PATENTS 6/1969 Otto 44/62 Primary Examiner-Patrick P. Garvin Assistant ExaminerMrs. Y. H. Smith Attorney, Agent, or Firm-Arthur G. Gilkes; William T. McClain; Philip Hill [57] ABSTRACT Fuel oil compositions, containing a pour depressant to provide a pour point below OF., exhibit improved pumpability as a result of the inclusion of a minor amount of certain styrenebutadiene copolymers.

3 Claims, No Drawings MIDDLE DISTILLATE FUEL OIL COMPOSITIONS HAVING IMPROVED PUMPABILITY CROSS-REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION In the storage and use of heavy and middle distillate fuel oils, problems connected with pour point are familiar to the art. The pour point of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled without disturbance under specified conditions. Pour point problems arise through the formation of solid or semi-solid waxy particles within an oil composition. For example, in the storage of fuel oils (e.g., heater oil or furnace oil) or diesel oil during the winter months, temperatures frequently are in the range of to --F. These low temperatures often cause crystallization or solidification of wax in the distillate oil.

One solution to the problem of handling oils below their natural pour point is to incorporate in the oil composition one of a wide number of known pour point depressants. In this manner it is possible to maintain flowability in a fuel even at very cold temperatures. It has been discovered, however, that pour point depressants alone are often notsufficient to permit effective handling of fuel oils at cold temperatures. This is because all hydrocarbon fuels yield crystals of solid wax as their temperature is lowered beyond the cloud point which is defined as the temperature at which paraffin wax or other solid substances begin to crystallize outor separate from solution when the oil is chilled under definite prescribed conditions (ASTM D 97). In many cases, even in the presence of a pour point depressant, the

crystals which form are sufficiently'dense so that an immobile layer of crystals is formed in the bottom of storage tanks and tends severely to clog pumps,f1lters and screens. Unfortunately, most pour point depressants tailored for middle distillate fuels are not effective in inhibiting such crystal growth or in modifying it in such a way as to maintain pumping capacity in the oil.

SUMMARY OF THE INVENTION This invention relates to fuel oil compositions having improved pumpability characteristics. More particularly, this invention relates to improving the pumpability of fuel oils which have already been modified to exhibit depressed pour points.

I have now discovered that certain copolymers of styrene and butadiene, when incorporated in pourdepressed middle distillate fuel compositions at a concentration ranging from 0.005 to 0.10 weight percent,

inhibit and/or modify the growth of solid wax crystals such that workable pumpabilities are maintained for the fuels even at very low temperatures.

The styrene-butadiene copolymers useful in this invention possess number average molecular weights no higher than about 5000 and contain from about 10 to about 40 weight percent styrene units.

DESCRIPTION OF THE INVENTION The middle distillate oils with which my invention is concerned may generally be described as distillates boiling in the range from 350 to 750F. and already modified to exhibit depressed pour points below 0F. These distillates may comprise virgin oils or cracked stocks derived, for example, from cycle oils boiling higher than gasoline. Examples of distillates suitable for use in this invention include diesel fuel (ASTM D975 ),jet fuel, fuel oils (ASTM D396), gas oils and the like. Of course, suitable distillates may additionally contain additives such as rust inhibitors, corrosion inhibitors, anti-oxidants and similar agents designed to impart a specific property to the oil.

Pour point depressantssuitable for modifying the middle distillates with which this invention is concerned, include any effective pour depressant known to the art. For example, such depressants may be ethylene/propylene, ethylene/vinyl acetate, ethylene/aminoalkyl ester, and ethylene/acrylic acid ester copolymers. A particularly effective pour depressant is an ethylene/acrylic ester/propylene terpolymer.

The styrene-butadiene copolymers which I have discovered'to be effective in improving the pumpability of the pour-depressed middle distillate oils described above range in styrene content from about 10 to about 40 weight percent and have a number average molecular weight less than 5,000. Inclusion of amounts as low as 0.005 weight percent of such copolymers in a pour point depressed middle distillate will result in improved pumpability. The amount of copolymer employed is preferably in the range 0.005 to 0.10 weight percent, and 0.01 weight percent is an especially effective amount.

EMBODIMENTS OF THE INVENTION To illustrate the effectiveness of the inclusion of a small amount of a styrene-butadiene copolymer in middle distillate fuel compositions, pumpability tests were run on No. 2 fuel oils containing pour point depressants. The pumpability test employed is designed to similate actual fuel handling conditions and is described as follows:

A tape wrapped 500 ml. leveling bulb is fitted at the top with a 3-way stopcock which is wired on. The bottom of the bulb is connected by a short strip of rubber tubing to the bottom of a J-shaped piece of three-sixteenths inch copper tubing 14 inches long. The top of the copper tubing is fitted with a brass union containing a 30-mesh screen soldered into a brass washer having a fifteen thirty-seconds inch opening. The level of the screen is at about the same height as the stopcock on the leveling bulb. A 250 ml. buret is connected to the brass union by rubber tubing.

To perform a test with this equipment, a 300 ml. fuel sample is poured into the leveling bulb and, with the stop-cock open, is subjected to one of the cooling sequences shown in Table I. When cooling is complete, a nitrogen pressure of 15 p.s.i.g. is introduced through the stopcock. A pumpability reading is obtained by measuring the delivery time in seconds between the 0 and 200 ml. marks on the measuring buret.

TABLE I GENERAL TEMPERATURE SEQUENCE Temperature, Degree, Farenheit Pumpability tests were run on two different fuel compositions each containing 0.04 weight percent of an ethylene/acrylic ester/propylene terpolymer as a pour point depressant. Fuel l was a No. 2 fuel oil having the following specifications:

Cloud point, F. -15

Pour point, F. 60

Gravity, APl 33.5 Fuel ll was a No. 2 fuel oil having the following specifications:

Cloud point, F. -5

Pour point, F. 40

Gravity, API 34.2 Each of the fuel compositions was tested alone and with 0.01 weight percent of a styrene-butadiene copolymer additionally present. All fuels were tested for a 20F. specification temperature. The results are presented in Table II.

0.01 wt.% -SB30 0.01 wt.% -SB40 0.0l wt.% -SBl0 None 0.01 wt.% -SB30 SB30 is a styrene-butadiene copolymer comprising 30 weight percent styrene and having a molecular weight of about 2,500. S840 is a styrene-butadiene copolymer comprising forty weight percent styrene and having a molecular weight of about 2,500. SBlO is a styrene-butadiene copolymer comprising ten weight percent styrene and having a molecular weight of about 2,500.

Each of the two fuel oils was additionally tested containing varying concentrations of the ester-based pour point depressant but containing no pumpability additive. In every case, the test apparatus became plugged and 200 ml. of the sample oil could not be delivered.

it is apparent from these data that pour-depressed fuels containing additionally a styrene-butadiene copolymer additive according to this invention show marked increases in pumpability and are suitable for storage and handling under very cold climatic conditions.

I claim:

1. A fuel composition having improved pumpability performance, comprising (a) a middle distillate fuel oil containing sufficient pour depressant additive to provide a pour point below 0F., and (b) from about 0.005 to about 0.10 weight percent of a styrene-butadiene copolymer having from about 10 to about 40 weight percent styrene units and having a number average molecular weight less than 5,000.

2. The composition of claim 1 wherein the amount of styrene-butadiene copolymer in the middle distillate fuel oil is about 0.01 weight percent;

3. The composition of claim 1 wherein the number average molecular weight of the styrene-butadiene copolymer is about 2,500. 

2. The composition of claim 1 wherein the amount of styrene-butadiene copolymer in the middle distillate fuel oil is about 0.01 weight percent.
 3. The composition of claim 1 wherein the number average molecular weight of the styrene-butadiene copolymer is about 2,
 500. 